Many fasteners are threaded into threaded holes. A variety of heads or ends are employed to be engaged by a tool and rotated to fasten or loosen. Some heads have cavities with flat drive flanks, such as Allen keys. The drive flanks may have a hexagonal configuration, in which case the tool has mating drive flanks. The tool may be simply an L-shaped rod with a hexagonal exterior. If due to rust or other conditions, the fastener is stuck, often the flanks of the tool will slip on the drive flats, failing to break the fastener loose.
Regardless of the type of fastener, a worker may have to resort to removing a stuck fastener in a “Dutchman fashion” by drilling a hole in the fastener. He would insert a Dutchman tool into the hole to grip the fastener and allow rotation in reverse. The Dutchman tool may be a tap with reverse threads, or the Dutchman tool may have jaws that expand in response to rotation of a cam member.